Fix 82 (#83)

## Description of changes
This PR tries to fix #82 by removing the unnecessary parens

## Relevant Issues

closes #82

Author: fdncred

.gitattributes

@@ -0,0 +1 @@
+* text=auto eol=lf

src/formatting.rs

@@ -334,7 +334,7 @@ impl<'a> Formatter<'a> {
                 self.format_closure_expression(*block_id, expr.span);
             }
             Expr::Subexpression(block_id) => {
-                self.format_subexpression(*block_id);
+                self.format_subexpression(*block_id, expr.span);
             }
 
             Expr::List(items) => self.format_list(items),
@@ -705,15 +705,33 @@ impl<'a> Formatter<'a> {
     }
 
     /// Format a subexpression
-    fn format_subexpression(&mut self, block_id: nu_protocol::BlockId) {
+    fn format_subexpression(&mut self, block_id: nu_protocol::BlockId, span: Span) {
         let block = self.working_set.get_block(block_id);
+        // Check if the subexpression has explicit parentheses in the source
+        let has_explicit_parens = self.source.get(span.start) == Some(&b'(')
+            && self.source.get(span.end - 1) == Some(&b')');
+        if !has_explicit_parens {
+            self.format_block(block);
+            return;
+        }
         // Special case: subexpressions containing only a string interpolation don't need parentheses
         if block.pipelines.len() == 1 && block.pipelines[0].elements.len() == 1 {
             if let Expr::StringInterpolation(_) = &block.pipelines[0].elements[0].expr.expr {
                 self.format_block(block);
                 return;
             }
         }
+        // Special case: subexpressions containing a pipeline starting with $in don't need parentheses
+        if block.pipelines.len() == 1 && !block.pipelines[0].elements.is_empty() {
+            let first_element = &block.pipelines[0].elements[0];
+            let element_text = String::from_utf8_lossy(
+                &self.source[first_element.expr.span.start..first_element.expr.span.end],
+            );
+            if element_text == "$in" {
+                self.format_block(block);
+                return;
+            }
+        }
 
         self.write("(");
         let is_simple = block.pipelines.len() == 1 && block.pipelines[0].elements.len() <= 3;

tests/fixtures/expected/def_with_pipeline_double_parens_issue82.nu

@@ -0,0 +1 @@
+def in-lang [ln] { $in | items {|k v| {$k: ($v | get $ln | default ($v | get 'en')) } } | reduce -f {} {|it acc| $acc | merge $it } }

tests/fixtures/expected/issue76.nu

@@ -1 +1 @@
-def pretty-print-command [] { ($"`(ansi default_dimmed)(ansi default_italic)($in)(ansi reset)`") }
+def pretty-print-command [] { $"`(ansi default_dimmed)(ansi default_italic)($in)(ansi reset)`" }

tests/fixtures/input/def_with_pipeline_double_parens_issue82.nu

@@ -0,0 +1 @@
+def in-lang [ln] { ($in | items {|k v| {$k: ($v | get $ln | default ($v | get 'en')) } } | reduce -f {} {|it acc| $acc | merge $it }) }

tests/ground_truth.rs

@@ -180,6 +180,12 @@ fn ground_truth_def_statement() {
     run_ground_truth_test(&test_binary, "def_statement");
 }
 
+#[test]
+fn ground_truth_def_with_pipeline() {
+    let test_binary = get_test_binary();
+    run_ground_truth_test(&test_binary, "def_with_pipeline_double_parens_issue82");
+}
+
 // ============================================================================
 // Ground Truth Tests - Control Flow
 // ============================================================================

toolkit.nu

@@ -6,7 +6,7 @@
 # (**2**) catch classical flaws in the new changes with *clippy* and (**3**)
 # make sure all the tests pass.
 # print the pipe input inside backticks, dimmed and italic, as a pretty command
-def pretty-print-command [] { ($"`(ansi default_dimmed)(ansi default_italic)($in)(ansi reset)`") }
+def pretty-print-command [] { $"`(ansi default_dimmed)(ansi default_italic)($in)(ansi reset)`" }
 # check standard code formatting and apply the changes
 export def fmt [--check, --verbose] {
     # do not apply the format changes, only check the syntax